CHARACTERIZING MODERN AND HOLOCENE BARRIER-ISLAND ENVIRONMENTS WITH FORAMINIFERAL ASSEMBLAGES: AN EXAMPLE FROM A WAVE-DOMINATED, MICROTIDAL BARRIER-ISLAND SYSTEM, NORTH CAROLINA, USA

Abstract

Abstract: Recent research has shown that sedimentological information in barrier-island settings may provide more detailed interpretations of some past coastal environments than interpretations based upon foraminifera. This research investigates whether targeted documentation of modern foraminifera in specific coastal environments can result in higher resolution micropaleontology-based paleoenvironmental reconstructions. Bear Island, North Carolina, characterized by little human disturbance, was chosen for detailed documentation of foraminifera in modern barrier-island-related environments. Modern sediments in all subenvironments were predominantly siliciclastic (< 30 % clastic carbonate debris) in composition: clastic carbonate allochems (e.g., mollusk shell fragments, echinoid spines) were admixed with fine- to medium-grained quartz sand. The hypothesis that modern foraminiferal assemblages of 26 modern coastal subenvironments can be distinguished based upon their foraminiferal assemblages was tested by discriminant analysis and resulted in the recognition of four environmental supergroups: shoreface, ebb-tidal delta, flood-tidal delta/inlet channel, and “barrier-combined” (foreshore, washover, dune, sandflat, spit, longshore bar, and trough). Holocene paleoenvironments represented by foraminiferal assemblages in 16 vibracores collected from the modern inner shelf, shoreface, ebb-tidal delta, and inlet environments of Bogue Banks, immediately adjacent to Bear Island, were interpreted, via discriminant analysis, based upon the modern dataset. Holocene and modern foraminiferal assemblages were similar but variations in species abundance and species diversity allowed for alternative paleoenvironmental classification of core samples at varying levels of probability. The methodology of this research is widely applicable to other coastal environments.